This invention relates to a vehicle traction control system and, more particularly, to such a system that includes limiting wheel spin by withholding fuel from selected cylinders of the engine by disabling selected fuel injectors in a port injected internal combustion engine.
Various methods have been proposed for preventing an excessive spinning condition of the driven wheels of a vehicle during vehicle acceleration when the operator initiated engine torque delivered to the vehicle driven wheels are such that the frictional forces between the tire and the road surface are overcome. These methods include the adjustment of engine torque and/or the application of the brakes of the driven wheels when an excessive acceleration spinning condition is detected. One method of adjusting engine torque output for limiting wheel spin during vehicle acceleration controls the individual injectors in a port injected internal combustion engine so as to selectively withhold fuel from selected cylinders. This disabling of cylinders reduces engine torque output to limit acceleration spin. In this form of system, the cylinders to which fuel is withheld intakes only air during their intake strokes. This air is then discharged into the exhaust system during the exhaust stroke of the cylinders where the air is mixed with the combustion gases discharged into the exhaust system from the operating cylinders.
In order to minimize the amounts of certain exhaust gas components, it is common in automotive vehicles to utilize a catalytic converter through which exhaust gases are discharged to the atmosphere and which is effective to oxidize carbon monoxides and hydrocarbons and to reduce nitrogen oxides. When the engine torque output is reduced by withholding fuel from one or more cylinders to limit excessive wheel spin in a vehicle in which the exhaust gases are discharged to the atmosphere through a catalytic converter, the air discharged into the exhaust system from the disabled cylinders combined with the combustion by-products of the operating cylinders creates a condition in which, the catalytic converter may be heated to excessive levels giving rise to a potential for damage to the catalytic converter. This is particularly the case when the engine is being operated in a power enrichment mode wherein the air/fuel ratio is rich resulting in a discharge of unburned hydrocarbons and carbon monoxide into the exhaust system which is then mixed with the oxygen-rich air discharged into the exhaust system from the disabled cylinders. The resulting oxidation of the hydrocarbons and carbon monoxides increase the temperature of the catalytic converter with the potential of excessive temperature conditions.
It would therefore be desirable to provide a method of protecting the catalytic converter in a traction control system wherein the engine torque output is restricted to prevent excessive wheel spin by selectively unfueling cylinders of the engine.